1. Field of the Invention
This invention relates to polyurethane elastomers of improved heat stability.
2. Description of the Prior Art
The invention concerns a process for the production of heat-resistant polyurethane elastomers in which an adduct containing terminal hydroxyl groups made from a primarily linear polyhydroxyl compound and polyisocyanate is reacted with a symmetrical aromatic diisocyanate in excess and chain extenders.
Polyurethane elastomers based on high-molecular-weight polyhydroxyl compounds, diisocyanates and low-molecular-weight chain extenders according to the state of the art are characterized by balanced set of properties and have therefore proved to be highly suitable in a number of applications.
Despite the advantages in their mechanical and wear properties, the polyurethane elastomers of the state of the art nevertheless have serious shortcomings which considerably restrict their applications.
This consists primarily of their inadequate heat stability, leading to early softening and thus the failure of highly stressed parts. This becomes especially undesirable when these parts are subjected to a dynamic load.
Polyurethane elastomers with improved heat stability thus far could be obtained only by the use of very costly and less common starting materials, such as naphthalene-1,5-diisocyanate, or toxic materials, such as methylene-bis(2-chloroaniline).